Soft buffer processing method and device in TDD systems

ABSTRACT

Methods, device, and User Equipment (UE) for processing a soft buffer, used in a Time Division Duplexing (TDD) system where uplink-downlink subframe distribution changes dynamically, are provided. A first method includes allocating, by a base station, transmission resources for a UE, and determining a parameter for processing a soft buffer, and performing rate matching for Physical Downlink Shared Channel (PDSCH); and sending, by the base station, data to the UE via Physical Downlink Control Channel (PDCCH) and PDSCH. The second method includes receiving, by a UE information of transmission resources allocated to the UE by a base station, and determining a parameter for processing a soft buffer; and receiving, by the UE, PDCCH and PDSCH sent by the base station according to the transmission resources and the parameter for processing the soft buffer.

PRIORITY

This application is a National Phase Entry of PCT InternationalApplication No. PCT/KR2013/002284, which was filed Mar. 20, 2013, andclaims priority to Chinese Patent Application Nos. 201210107431.9 and201210273508.X, which were filed on Apr. 12, 2012 and Aug. 2, 2012,respectively, in the Chinese Intellectual Property Office, the contentsof which are incorporated herein by reference.

BACKGROUND 1. Field of the Invention

The present invention relates generally to the field of mobilecommunications, and more particularly, to a soft buffer processingmethod and device in TDD systems.

2. Description of the Related Art

A Long Term Evolution (LTE) system supports Time Division Duplexing(TDD). A frame structure of a TDD system is shown in FIG. 1. The lengthof each radio frame is 10 ms, and each radio frame is equally split intotwo half-frames with 5 ms length. Each half-frame contains 8 timeslotsof 0.5 ms length and 3 special fields, i.e. Downlink Pilot Time Slot(DwPTS), Guard Period (GP), and Uplink Pilot Time Slot (UpPTS), thetotal length of these 3 special fields being 1 ms. Each subframeconsists of two consecutive timeslots, i.e. kth subframe containingtimeslots 2k and 2k+1. A TDD system supports 7 uplink-downlinkconfigurations, as shown in Table 1. Here, D represents a downlinksubframe, U represents an uplink subframe, and S represents the specialsubframe containing the 3 special fields.

TABLE 1 LTE TDD Uplink-Downlink Configurations Config- urationSwitch-point Subframe number Number periodicity 0 1 2 3 4 5 6 7 8 9 0  5ms D S U U U D S U U U 1  5 ms D S U U D D S U U D 2  5 ms D S U D D D SU D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms DS U D D D D D D D 6 10 ms D S U U U D S U U D

LTE TDD Uplink-Downlink Configurations

In the LTE TDD system, for downlink data Hybrid Automatic Repeat reQuest(HARQ) transmission, a Physical Downlink Control Channel (PDCCH) isconfigured to schedule a Physical Downlink Shared Channel (PDSCH) in acurrent subframe; and Acknowledged/Not Acknowledged (ACK/NACK)information corresponding to the PDSCH or the PDCCH indicating downlinkSemi-Persistent Scheduling release (SPS release) in 0, 1, or moredownlink subframes can be fed back in one uplink subframe n, the indexesof these downlink subframes being n-k, where k belongs to a set K andthe set K is decided by the uplink-downlink configuration and the uplinksubframe n. Table 2 discloses HARQ timing relations defined in the LTErelease 8 system.

TABLE 2 Index Set K Uplink-downlink Subframe index n configuration 0 1 23 4 5 6 7 8 9 0 — — 6 — 4 — — 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8,7, 4, 6 — — — — 8, 7, — — 4, 6 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — —12, 8, 7, 11 6, 5, 4, 7 — — — — — — 5 — — 13, 12, 9, 8, — — — — — — — 7,5, 4, 11, 6 6 — — 7 7 5 — — 7 7 —

According to the above HARQ timing relations, the maximum numbers ofdownlink HARQ processes corresponding to the above 7 TDD uplink-downlinkconfigurations are different. Here, for each TDD uplink-downlinkconfiguration, the maximum number of downlink HARQ processes is used toguarantee the base station identifying respective parallel HARQprocesses without confusion by using the HARQ process indexes in thePDCCH.

TABLE 3 Uplink-downlink Maximum number of downlink configuration HARQprocesses 0 4 1 7 2 10 3 9 4 12 5 15 6 6

HARQ timing relations of the LTE TDD system are described above, andanother question related to HARQ is how to process a soft buffer. Infact, User Equipments (UEs) are divided into multiple UE categoriesaccording to their processing capacity, and the division is based onwhether a UE supports Multiple-Input Multiple-Output (MIMO), the maximumnumber of MIMO data streams supported, the size of the soft buffer, etc.Here, the soft buffer is used to save received soft bits when the UE isunable to decode data sent from the base station properly, and canperform soft combination during HARQ retransmission, thus improving thelink performance.

The process of the soft buffer influences Rate Matching (RM) of downlinkdata at the base station side. In the LTE TDD release 10, the size of asoft buffer of a UE is denoted N_(soft), and no matter if the UE is inthe single carrier mode or in the carrier aggregation mode, for eachcode block of a transport block, rate matching is performed according tothe size of the soft buffer

${N_{cb} = {\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}},$where C is the total number of code blocks divided from the transportblock, K_(w) is the total number of encoding bits output by turboencoding,

${N_{IR} = \left\lfloor \frac{N_{soft}}{K_{C} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ},M_{limit}} \right)}} \right\rfloor},$K_(MIMO) depends on the transmission mode of the UE, for MIMOtransmission mode, K_(MIMO)=2, for non-MIMO transmission mode,K_(MIMO)=1, M_(DL_HARQ) is the maximum number of downlink HARQ processesgiven in Table 3, M_(limit) is a constant equal to 8, and K_(C) is aconstant related to the UE capacity category. That is to say, no matterhow many carriers the UE actually works at, when the rate matching isperformed, the same method as the UE only configuring the current onecarrier is used to perform the rate matching.

At the UE side, when the UE incorrectly decodes a code block, it mustkeep soft bits for the code block, so that HARQ soft combination can beperformed, thus improving the link performance. To better support HARQIncremental Redundancy (IR), the base station must know which soft bitshave been actually stored when the UE is unable to decode the code blockcorrectly. In the LTE TDD Release 10, the method of UE processing a softbuffer is allocating its soft buffer equally to one or more cellscurrently being configured. The number of carriers configured by the UEis denoted N_(cells) ^(DL), and for each cell, for at leastK_(MIMO)·min(M_(DL_HARQ),M_(limit)) transport blocks, when the decodingof a code block of a transport block has failed, soft bits w_(k)w_(k+1), . . . , w_(mod(k+n) _(SB) _(−1,N) _(tb) ) must be kept by theUE for this code block as specified in LTE Advanced (LTE-A), where

${n_{SB} = {\min\left( {N_{cb},\left\lfloor \frac{N_{soft}}{C \cdot N_{cells}^{DL} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ},M_{limit}} \right)}} \right\rfloor} \right)}},$w_(k) is a soft bit received by the UE, and k is the relative smallerindex of indexes of respective soft bits received by the UE.

In the current LTE system specification, the uplink-downlinkconfiguration adopted by a cell is configured via broadcast signaling,i.e., contained in the System Information Block 1 (SIB1). Therefore, theLTE system supports changing the uplink-downlink configuration onceevery 640 nm at the fastest, and changing the system information 32times in 3 hours at most in the current specification. To quickly adaptto changes of service characteristics, currently the 3rd GenerationPartnership Project (3GGP) organization is studying how to supportchanging the system uplink-downlink subframe allocation at a fasterspeed. For example, support changing the uplink-downlink configurationat a faster speed, e.g. changing once every 200 ms; or changing theuplink-downlink subframe configuration at an order of time with radioframe length being 10 ms. In fact, the base station scheduler changesthe uplink-downlink subframe distribution according to servicerequirements, and adopts certain scheduling restrictions to sustainsystem normal working, while the UE may not need to know which of the 7uplink-downlink configurations it is working at. Even the actual workinguplink-downlink subframe distribution can be unlimited to the aboveseven configurations in Table 1, and above all, the actualuplink-downlink subframe distribution can be transparent to the UE. Thechange of the uplink-downlink subframe distribution adopted by this kindof cell influences HARQ-ACK timing relation during downlinktransmission, resulting in the change of the maximum number of downlinkHARQ processes, and accordingly influences processing of soft buffer ofdata during the HARQ transmission.

SUMMARY

The present invention has been made to address the above-mentionedproblems and disadvantages, and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present inventionprovides a method of and device for processing a soft buffer whenchanging allocation for an uplink-downlink subframe of a TDD system.

In accordance with an aspect of the present invention, a method ofprocessing soft buffer, used in a Time Division Duplexing (TDD) systemwhere uplink-downlink subframe distribution changes dynamically, isprovided. The method includes allocating, by a base station,transmission resources for a User Equipment (UE), and determining aparameter for processing a soft buffer, and performing rate matching forPhysical Downlink Shared Channel (PDSCH); and sending, by the basestation, data to the UE via Physical Downlink Control Channel (PDCCH)and PDSCH.

In accordance with another aspect of the present invention, a method ofprocessing soft buffer, used in a Time Division Duplexing (TDD) systemwhere uplink-downlink subframe distribution changes dynamically, isprovided. The method includes receiving, by a User Equipment (UE),information of transmission resources allocated to the UE by a basestation, and determining a parameter for processing a soft buffer; andreceiving, by the UE, Physical Downlink Control Channel (PDCCH) andPhysical Downlink Shared Channel (PDSCH) sent by the base stationaccording to the transmission resources and the parameter for processingthe soft buffer.

In accordance with another aspect of the present invention a basestation side device, used in a Time Division Duplexing (TDD) systemwhere uplink-downlink subframe distribution changes dynamically, isprovided. The base station side device includes a resource managementmodule configured to allocate transmission resources for a UserEquipment (UE) and determine a parameter for processing a soft buffer;and a sending module configured to perform rate matching for PhysicalDownlink Shared Channel (PDSCH) and send data to the UE via PhysicalDownlink Control Channel (PDCCH) and PDSCH.

In accordance with another aspect of the present invention a UserEquipment (UE), used in a Time Division Duplexing (TDD) system whereuplink-downlink subframe distribution changes dynamically, is provided.The UE includes a resource management module configured to determineinformation of transmission resources allocated to it by a base station,and determine a parameter for processing a soft buffer; and a receivingmodule configured to receive Physical Downlink Control Channel (PDCCH)and Physical Downlink Shared Channel (PDSCH) sent by the base stationaccording to the transmission resources and the parameter for processingthe soft buffer. In accordance with another aspect of the presentinvention a method of supporting downlink transmission, used in a TimeDivision Duplexing (TDD) system where uplink-downlink subframedistribution changes dynamically, is provided. The method includesreceiving, by a User Equipment (UE), information sent by a base stationvia Physical Downlink Shared Channel (PDCCH) and Physical DownlinkShared Channel (PDSCH) based on transmission resources allocated by abase station; and feeding back, by a UE, Hard-Acknowledgement (HARQ-ACK)information to the base station according to a reference HARQ-ACK timingrelation, wherein a reference HARQ-ACK timing relation defines aHARQ-ACK feedback timing of subframes applicable to downlinktransmission during downlink transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following detailed description,taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a TDD system frame structure;

FIG. 2 is a schematic diagram of reference HARQ-ACK timing;

FIG. 3 is a flowchart of a method of base station side processing of asoft buffer according to an embodiment of the present invention;

FIG. 4 is a flowchart of a method of terminal side processing of a softbuffer according to an embodiment of the present invention; and

FIG. 5 is a schematic diagram of the base station side device and UEstructures according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

To make the objects and technical solutions of the present inventionclear and understandable, further detailed description is provided forthe present invention by reference to the drawings and embodiments ofthe present invention.

According to the above present invention, for a TDD system where theuplink-downlink subframe distribution can be changed quickly ordynamically, according to different instruction methods adopted, the UEmay know which configuration it is currently working at, the UE may notknow actual allocation for the current uplink-downlink subframe, or theactual distribution for the working uplink-downlink subframe can bedifferent from the existed uplink-downlink configurations. The basestation scheduler guarantees normal proceeding of uplink-downlink datatransmission. The change of the uplink-downlink subframe distribution ofa cell influences the HARQ-ACK timing relation of downlink transmission,resulting in the change of the actual maximum number of downlink HARQprocesses, and accordingly influences processing of soft buffer of dataduring the HARQ transmission by a base station and a UE. In thefollowing description, a UE supporting the function of flexibleconfiguration for uplink-downlink subframe is called a new UE, andcorrespondingly, a UE that does not support the function of flexibleconfiguration for uplink-downlink subframe is called an old UE. For anold UE, uplink-downlink data is transmitted according to the basic TDDuplink-downlink configuration configured by the SIB1 broadcastinformation.

One possible method of defining a HARQ-ACK timing relation of downlinktransmission is defining the HARQ-ACK timing relation by complying witha reference HARQ-ACK timing relation, independent of actual distributionfor currently running uplink-downlink subframe and the basic TDDuplink-downlink configuration configured by the SIB1 broadcastinformation. For a new UE, for the subframes whose HARQ-ACK timing hasbeen defined in the reference HARQ-ACK timing relation, the HARQ-ACKfeedback timing of such subframes will be determined according to thisreference HARQ-ACK timing relation. For example, the HARQ-ACK feedbacktiming corresponding to all subframes that can be possible to be fixedas downlink subframes or subframes that can be flexibly changed intodownlink subframes during the actual running is defined in the referenceHARQ-ACK timing relation, so that the downlink transmission of the newUE is performed according to HARQ-ACK feedback timing positions got fromthe reference HARQ-ACK timing relation. Specifically, the set ofsubframes of the cell that may work at downlink direction during actualrunning is denoted K_(working), the set of downlink subframes withHARQ-ACK feedback timing being defined in the reference timing relationis denoted K_(ref), then the selection of a reference timing relationguarantees K_(working) being a subset of K_(ref). It is worthy of notingthat K_(working) can be the same as K_(ref); i.e., the biggest subset ofK_(ref) is itself. To simplify the system operation, a possible methodof defining a reference HARQ-ACK timing relation is reusing a HARQ-ACKtiming relation of an existing uplink-downlink configuration, e.g. oneof the 7 configurations in Table 1, accordingly, and the referenceHARQ-ACK timing relation can be got from Table 2.

As shown in FIG. 2, HARQ-ACK timing in conventional TDD uplink-downlinkconfiguration 2 is adopted as the above reference HARQ-ACK timingrelation, i.e. the HARQ-ACK feedback timing of downlink transmission insubframes 9, 0, 1, and 3 is in subframe 7. Specifically, if the currentworking TDD uplink-downlink configuration is uplink-downlinkconfiguration 0, then the UE detects downlink transmission in subframes0 and 1 at most, and according to the reference HARQ-ACK timingrelation, the HARQ-ACK information of these 2 subframes will all be fedback in subframe 7; if the current working TDD uplink-downlinkconfiguration is uplink-downlink configuration 1, then the UE detectsthe downlink transmission in subframes 9, 0, and 1 at most, andaccording to the reference HARQ-ACK timing relation, the HARQ-ACKinformation of these 3 subframes will all be fed back in subframe 7; ifthe current working TDD uplink-downlink configuration is 6, then the UEdetects the downlink transmission in subframes 9, 0, and 1 at most, andaccording to the reference HARQ-ACK timing relation, the HARQ-ACKinformation of these 3 subframes will all be fed back in the subframe 7;and if the current working TDD uplink-downlink configuration is 2, thenthe UE detects the downlink transmission in subframes 9, 0, 1, and 3 atmost, and according to the reference HARQ-ACK timing relation, theHARQ-ACK information of these 4 subframes will all be fed back in thesubframe 7. Actually, when the base station flexibly configures thedirection of subframes, the TDD uplink-downlink subframe distributionworking at a certain period is not necessary to be limited to one of thetraditional uplink-downlink configurations, however, according to theHARQ-ACK timing relation of the TDD uplink-downlink configuration 2, theHARQ-ACK information of the downlink transmission of subframes 9, 0, 1and 3 is always fed back in subframe 7.

The above reference timing relation can be configured via high levelsignaling including a cell specific broadcast signal or a UE specificRadio Resource Control (RRC) signaling; or the above reference timingrelation is predefined, for example, predefining it as the HARQ timingrelation of the TDD uplink-downlink configuration 2 for the systemsupporting the changes of the uplink-downlink subframe distribution.Alternatively, for the above reference timing relation, the timingrelation of a traditional TDD uplink-downlink configuration can beuniquely determined as the reference timing relation when the cell isworking in a flexible subframe mode according to the TDD uplink-downlinkconfiguration sent in the broadcast information block SIB1, e.g., theTDD uplink-downlink configuration used as reference timing can bedefined in a table for each uplink-downlink configuration in thebroadcast information block SIB1.

When a cell changes from one uplink-downlink configuration to anotheruplink-downlink configuration, the maximum number of downlink HARQprocesses will change accordingly, and at a border of the change of thenew and old uplink-downlink configurations, the actual maximum number ofdownlink HARQ processes may be different from the maximum numbers ofdownlink HARQ processes of the old and new uplink-downlinkconfigurations. In addition, when the base station changes theuplink-downlink subframe distribution, a UE may not know the actualcurrently running uplink-downlink subframe distribution, but onlydepends on a base station scheduler to guarantee the uplink-downlinkdata transmission proceeding properly, which means that the UE has noway to actually know the maximum number of the current actual downlinkHARQ processes. Since the base station and the UE processing the softbuffer depends on the maximum number of HARQ processes of the cell, sowhen the uplink-downlink subframe distribution of the cell changes, thebase station and the UE operating the soft buffer will definitely beaffected. The method of processing soft buffer described by the presentinvention hereafter can be used together with the above method ofdetermining the HARQ-ACK feedback timing by defining the referenceHARQ-ACK timing relation of the present invention, but is not limited tothis method of determining the HARQ-ACK feedback timing of downlinktransmission.

FIG. 3 is a flow chart of a method of a base station processing a softbuffer according to the present invention, including the followingsteps.

In step 301, a terminal device allocates transmission resources for theUE and determines the parameters of processing a soft buffer.

In step 301, the base station allocates transmission resources for theUE, determines parameters of processing a soft buffer, and then performsrate matching for the physical downlink sharing channel PDSCH.

In an embodiment of the present invention, a processing method includes,when the uplink-downlink subframe distribution of a cell changes,determining the current actual maximum number of downlink HARQprocesses, and according to this actual maximum number of downlink HARQprocesses, processing a soft buffer. For example, the current actualmaximum number of downlink HARQ processes of a cell is denotedM_(DL_HARQ) ^(real), and based on the base station rate matching methoddefined in the current LTE TDD Release 10, the actual maximum number ofdownlink HARQ processes M_(DL_HARQ) ^(real) is used to calculate thesoft buffer allocated to each code block. The size of the soft buffer ofthe UE is denoted N_(soft), then when the base station performs ratematching for each code block of a transport block, the size of the softbuffer of the code block is

${N_{cb} = {\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}},$where C is the total number of code blocks divided from the transportblock, K_(w) is the total number of encoding bits output by turboencoding,

${N_{IR} = \left\lfloor \frac{N_{soft}}{K_{C} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{real},M_{limit}} \right)}} \right\rfloor},$where K_(MIMO) depends on the transmission mode of the UE, for MIMOtransmission mode, K_(MIMO)=2, for non-MIMO transmission mode,K_(MIMO)=1, M_(limit) is a constant equal to 8, and K_(C) is a constantrelated to the category of UE capacity. Thus, the hale station performsrate matching for the UE data based on the size of the soft buffer

${N_{cb} = {\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}},$

Corresponding to the operations at the base station, there are manymethods of the UE processing a soft buffer, and a method of the UEprocessing a soft buffer based on M_(DL_HARQ) ^(real) is describedhereafter. At the UE side, based on the method of the UE processing asoft buffer as defined in LTE TDD Release 10, the UE can equallyallocate its soft buffer to multiple cells which are configured by thebase station for the UE to work in, and for each cell, for at leastK_(MIMO)·min(M_(DL_HARQ) ^(real),M_(limit)) transport blocks, when thedecoding of a code block of a transport block fails, the number of softbits kept for this code block is at least

${n_{SB} = {\min\left( {N_{cb},\left\lfloor \frac{N_{soft}}{C \cdot N_{cells}^{DL} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{real},M_{limit}} \right)}} \right\rfloor} \right)}},$where, N_(cells) ^(DL) is the number of cells that the base stationconfigures for the UE to work in. Specifically, these soft bits aredenoted w_(k) w_(k+1), . . . , w_(mod(k+n) _(SB) _(−1,N) _(cb) ₎, wherew_(k) is a soft bit received by the UE, and k is the smallest index ofthe indexes of the respective soft bits received by the UE. The basestation can be based on the above method of the UE keeping soft bits forthe code block so as to optimize retransmission operation of the HARQwith incremental redundancy (HARQ IR).

Based on the above HARQ-ACK timing relation of downlink transmission ofthe cell by adopting a reference HARQ-ACK timing relation, the maximumnumber of downlink HARQ processes determined according to the referenceHARQ-ACK timing relation is denoted M_(DL_HARQ) ^(ref). According to anembodiment of the present invention, another processing method processesa soft buffer by using the maximum number of downlink HARQ processesM_(DL_HARQ) ^(ref) determined according to the reference HARQ-ACK timingrelation, independent of the basic TDD uplink-downlink configurationconfigured in SIB1 broadcast information or actual distribution forcurrent uplink-downlink subframe of the cell. In this case, if themethod of defining the reference HARQ-ACK timing relation is reusing aHARQ-ACK timing relation of a traditional uplink-downlink configuration,e.g., any of the 7 downlink configurations as shown in Table 1, thenaccordingly, M_(DL_HARQ) ^(ref) can be got from Table 3. For example,based on the method of base station rate matching defined in the LTE TDDrelease 10, M_(DL_HARQ) ^(ref) is used to calculate the soft bufferallocated to each code block. When the base station performs ratematching for each code block of a transport block, the size of the softbuffer of the code block is

${N_{cb} = {\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}},$where C is the total number of code blocks divided from the transportblock, K_(w) is the total number of encoding bits output by turboencoding,

${N_{IR} = \left\lfloor \frac{N_{soft}}{K_{C} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{ref},M_{limit}} \right)}} \right\rfloor},$where K_(MIMO) depends on the transmission mode of the UE, and for MIMOtransmission mode, K_(MIMO)=2, for non-MIMO transmission mode,K_(MIMO)=1, M_(limit) is a constant equal to 8, and K_(C) is a constantrelated to the category of UE capacity. Thus, the base station performsrate matching for the UE data according to the size of soft buffer

$N_{{cb} =}{{\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}.}$

Corresponding to the operations at the base station, there are manymethods of processing a soft buffer for the UE, and a method of the UEprocessing a soft buffer based on M_(DL_HARQ) ^(ref), is describedhereafter. At the UE side, based on the method of UE processing a softbuffer defined in the current LTE TDD release 10, the UE can equallyallocate its soft buffer to multiple cells which are configured by thebase station for the UE to work in, and for each cell, and for at leastK_(MIMO)·min(M_(DL_HARQ) ^(ref), M_(limit)) transport blocks, when thedecoding of a code block of a transport block fails, the number of softbits kept for this code block is at least

${n_{SB} = {\min\left( {N_{cb},\left\lfloor \frac{N_{soft}}{C \cdot N_{cells}^{DL} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{ref},M_{limit}} \right)}} \right\rfloor} \right)}},$where N_(cells) ^(DL) is the number of cells that the base stationconfigures for the UE to work in. Specifically, these soft bits aredenoted w_(k) w_(k+1), . . . , w_(mod(k+nSB-1, Ncb)), where w_(k) is asoft bit received by the UE, and k is the smallest index of the indexesof the respective soft bits received by the UE. The base station can bebased on the above method of the UE keeping soft bits for the code blockso as to optimize the retransmission operation of HARQ with incrementalredundancy (HARQ IR).

It should be understood that, when the base station processes a softbuffer based on any of the parameters M_(DL_HARQ) ^(real), M_(DL_HARQ)^(base), X and M_(DL_HARQ) ^(ref), the UE side can also process a softbuffer based on any of the parameters M_(DL_HARQ) ^(real), M_(DL_HARQ)^(base), X and M_(DL_HARQ) ^(ref). It shall be understood that the abovecombination can be joined and selected freely as required. If the basestation and the UE adopt the same parameter for processing a softbuffer, then the operation consistency can be kept; and if the basestation and the UE adopt different parameters for processing a softbuffer, then the optimization can be performed under differentconditions.

In step 302, the base station sends data to the UE via PDCCH and PDSCH.

Afterwards, the UE receives the PDSCH sent by the base station,determines the parameter for processing a soft buffer; and when thePDSCH decoding verification fails, performs caching for soft bits of thePDSCH.

Corresponding to the method employed by the base station side, thepresent invention further includes a method of the UE processing a softbuffer. FIG. 4 is a flow chart showing a method of processing a softbuffer of the present invention, including the following steps.

In step 401, the UE receives information of transmission resourcesallocated to it by the base station, and determines the parameter forprocessing a soft buffer.

In an embodiment of the present invention, a processing method includes,when the uplink-downlink subframe distribution of the cell changes,determining the current actual maximum number of downlink HARQprocesses, and processing a soft buffer according to this actual maximumnumber of downlink HARQ processes. The actual maximum number of HARQprocesses of a cell is denoted M_(DL_HARQ) ^(real).

There are many methods of processing a soft buffer for the base station,and a method of the base station processing a soft buffer based onM_(DL_HARQ) ^(real) is described hereafter. Based on the method of ratematching of the base station defined in the current LTE TDD release 10,a soft buffer allocated to each code block is calculated by using thisactual maximum HARQ process number M_(DL_HARQ) ^(real). The size of thesoft buffer of the UE is denoted N_(soft), then when the base stationperforms rate matching for each code block of a transport block, thesize of the soft buffer of the code block is

${N_{cb} = {\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}},$where C is the total number of code blocks divided from a transportblock, K_(w), is the total number of encoding bits output by turboencoding,

${N_{IR} = \left\lfloor \frac{N_{soft}}{K_{C} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{real},M_{limit}} \right)}} \right\rfloor},$where K_(MIMO) depends on the transmission mode of the UE, for MIMOtransmission mode, K_(MIMO)=2, for non-MIMO transmission mode,K_(MIMO=1), M_(limit) is a constant equal to 8, and K_(C) is a constantrelated to the category of the UE capacity.

At the UE side, based on the method of the UE processing a soft bufferdefined in the current LTE TDD release 10, the UE can equally allocateits soft buffer to multiple cells which are configured by the basestation for the UE to work in, and for at least K_(MIMO)·min(M_(DL_HARQ)^(real),M_(limit)) transport blocks, when the decoding of a code blockof a transport block fails, the number of soft bits kept for this codeblock is at least

${n_{SB} = {\min\left( {N_{cb},\left\lfloor \frac{N_{soft}}{C \cdot N_{cells}^{DL} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{real},M_{limit}} \right)}} \right\rfloor} \right)}},$where N_(cells) ^(DL) is the number of cells that the base stationconfigures for the UE to work in. Specifically, these soft bits aredenoted w_(k) w_(k+1), . . . , w_(mod(k+nSB-1, Ncb)), where w_(k) is asoft bit received by the UE, and k is the smallest index of the indexesof the respective soft bits received by the UE. Thus, the UE can keepsoft bits in the soft buffer for each code block according to the abovemethod so as to support the retransmission operation of HARQ withincremental redundancy (HARQ IR).

The above method processes a soft buffer based on the actual maximumnumber of downlink HARQ transmission processes M_(DL_HARQ) ^(real), itsperformance is optimal but the complexity thereof is relatively high.For example, in certain circumstances, according to specified or agreedupon specifications, the UE obtains the actual maximum number ofdownlink HARQ transmission processes M_(DL_HARQ) ^(real). In addition,to lower complexity, the present invention discloses the followingmethod to support more application scenarios.

In the LTE TDD system, a basic TDD uplink-downlink configuration isindicated in the broadcast information block SIB1, all UEs in the cellcan receive this broadcast information, but old UEs can only determinethe HARQ-ACK timing and the maximum number of downlink HARQ processesM_(DL_HARQ) ^(real) according to this basic TDD uplink-downlinkconfiguration, and process a soft buffer accordingly. The new UE notonly can receive broadcasting information of this basic TDDuplink-downlink configuration, but also can receive other controlinformation related to the uplink-downlink subframe distribution. In anembodiment of the present invention, a method is disclosed for a new UEto process a soft buffer based on the maximum number of downlink HARQprocesses M_(DL_HARQ) ^(base) defined in the LTE Release 8 for the basicTDD uplink-downlink configuration of the SIB1 broadcast information.

There are many methods of processing a soft buffer for the base station,and a method of the base station processing a soft buffer based on isdescribed hereafter. Based on the rate matching method of a base stationdefined in the current LTE TDD release 10, a soft buffer allocated toeach code block is calculated using this actual maximum HARQ processnumber M_(DL_HARQ) ^(base). The size of the soft buffer of the UE isdenoted N_(soft), then when the base station performs rate matching foreach code block of a transport block, the size of the soft buffer of thecode block is

${N_{cb} = {\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}},$where C is the total number of code blocks divided from a transportblock, K_(w) is the total number of encoding bits output by turboencoding,

${N_{IR} = \left\lfloor \frac{N_{soft}}{K_{C} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{base},M_{limit}} \right)}} \right\rfloor},$where K_(MIMO) depends on the transmission mode of the UE, for MIMOtransmission mode, K_(MIMO)=2, for non-MIMO transmission mode,K_(MIMO)=1, M_(limit) is a constant equal to 8, and K_(C) is a constantrelated to the category of UE capacity.

At the UE side, based on the method of the UE processing a soft bufferdefined in the current LTE TDD release 10, the UE can equally allocateits soft buffer to multiple cells which are configured by the basestation for the UE to work in, and for at least K_(MIMO)·min(M_(DL_HARQ)^(base),M_(limit))

transport blocks, when the decoding of a code block of a transport blockfails, the number of soft bits kept for this code block is at least

${n_{SB} = {\min\left( {N_{cb},\left\lfloor \frac{N_{soft}}{C \cdot N_{cells}^{DL} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{base},M_{limit}} \right)}} \right\rfloor} \right)}},$where N_(cells) ^(DL) is the number of cells that the base stationconfigures for the UE to work in. Specifically, these soft bits aredenoted w_(k) w_(k+1), . . . , w_(mod(k+nSB-1,Ncb)), where w_(k) is asoft bit received by the UE, and k is the smallest index of the indexesof the respective soft bits received by the UE. The base station can bebased on the above method of UE keeping soft bits for the code block soas to support the retransmission operation of HARQ with incrementalredundancy (HARQ IR).

In an embodiment of the present invention, a method is disclosed forprocessing a soft buffer based on substituting a predefined value X intothe maximum number of downlink HARQ processes independent of the basicTDD uplink-downlink configuration configured in SIB1 broadcastinformation or actual distribution for current uplink-downlink subframeof the cell. This predefined value can be configured by a high layersemi-statically, and can also be a fixed value in the standards. Forexample, the predefined value X is equal to 8. For Frequency DivisionDuplex (FDD), the maximum number of downlink HARQ processes is fixed tobe 8, and the soft buffer is processed based on X being equal to 8, sothat the downlink performance matches the FDD system.

There are many methods of processing a soft buffer for the base station,and a method of the base station processing a soft buffer based on X isdescribed hereafter. Based on the method of base station rate matchingdefined in the current LTE TDD release 10, the soft buffer allocated toeach code block is calculated using the predefined X. When the basestation performs rate matching for each code block of a transport block,the size of the soft buffer of the code block is

${N_{cb} = {\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}},$where C is the total number of code blocks divided from a transportblock, K_(w), is the total number of encoding bits output by turboencoding,

${N_{IR} = \left\lfloor \frac{N_{soft}}{K_{C} \cdot K_{MIMO} \cdot {\min\left( {X,M_{limit}} \right)}} \right\rfloor},$where K_(MIMO) depends on the transmission mode of the UE, for MIMOtransmission mode, K_(MIMO)=2, for non-MIMO transmission mode,K_(MIMO)=1, M_(limit) is a constant equal to 8, and K_(C) is a constantrelated to the category of the UE capacity.

At the UE side, based on the method of the UE processing a soft bufferdefined in the current LTE TDD release 10, the UE can equally allocateits soft buffer to multiple cells which are configured by the basestation for the UE to work in, and for at least transport blocks, whenthe decoding of a code block of a transport block fails, the number ofsoft bits kept for this code block is at least

${n_{SB} = {\min\left( {N_{cb},\left\lfloor \frac{N_{soft}}{C \cdot N_{cells}^{DL} \cdot K_{MIMO} \cdot {\min\left( {X,M_{limit}} \right)}} \right\rfloor} \right)}},$where N_(cells) ^(DL) is the number of cells that the base stationconfigures for the UE to work in. Specifically, these soft bits aredenoted w_(k) w_(k+1), . . . , w_(mod(k+nSB-1, Ncb)), where w_(k) is asoft bit received by the UE, and k is the smallest index of the indexesof the respective soft bits received by the UE. Thus, the UE can keepsoft bits in the soft buffer for each code block according to the abovemethod so as to support the HARQ with incremental redundancy (HARQ IR).

Based on the above method of defining a HARQ-ACK timing relation ofdownlink transmission of the cell by adopting a reference HARQ-ACKtiming relation, the maximum number of downlink HARQ processesdetermined according to the reference HARQ-ACK timing relation isdenoted M_(DL_HARQ) ^(ref). According to an embodiment of the presentinvention, a soft buffer is processed by using the maximum number ofdownlink HARQ processes M_(DL_HARQ) ^(ref) determined according to thereference HARQ-ACK timing relation independent of the basic TDDuplink-downlink configuration configured in SIB1 broadcast informationor current actual uplink-downlink subframe distribution of the cell. Inthis case, if the method of defining the reference HARQ-ACK timingrelation is reusing a HARQ-ACK timing relation of a traditionaluplink-downlink configuration, e.g., any of the 7 downlinkconfigurations as shown in Table 1, then accordingly, M_(DL_HARQ) ^(ref)can be got from Table 3. For example, based on the method of basestation rate matching defined in the LTE TDD release 10, M_(DL_HARQ)^(ref) is used to calculate the soft buffer allocated to each codeblock.

There are many methods of processing a soft buffer for the base station,and a method of the base station processing a soft buffer based onM_(DL_HARQ) ^(ref) is described hereafter. When the base stationperforms rate matching for each code block of a transport block, thesize of the soft buffer of the code block is

${N_{cb} = {\min\left( {\left\lfloor \frac{N_{IR}}{C} \right\rfloor,K_{w}} \right)}},$where C is the total number of code blocks divided from a transportblock, K_(w) is the total number of encoding bits output by turboencoding,

${N_{IR} = \left\lfloor \frac{N_{soft}}{K_{C} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{ref},M_{limit}} \right)}} \right\rfloor},$where K_(MIMO) depends on the transmission mode of the UE, for MIMOtransmission mode, K_(MIMO)=2, for non-MIMO transmission mode,K_(MIMO)=1, M_(limit) is a constant equal to 8, and K_(C) is a constantrelated to the category of the UE capacity.

At the UE side, based on the method of UE processing a soft bufferdefined in the current LTE TDD release 10, the UE can equally allocateits soft buffer to multiple cells which are configured by the basestation for the UE to work in, and for at least K_(MIMO)·min(M_(DL_HARQ)^(ref)·M_(limit)) transport blocks, when the decoding of a code block ofa transport block fails, the least number of soft bits kept for thiscode block is

${n_{SB} = {\min\left( {N_{cb},\left\lfloor \frac{N_{soft}}{C \cdot N_{cells}^{DL} \cdot K_{MIMO} \cdot {\min\left( {M_{DL\_ HARQ}^{ref},M_{limit}} \right)}} \right\rfloor} \right)}},$where N_(cells) ^(DL) is the number of cells that the base stationconfigures for the UE to work in. Specifically, these soft bits aredenoted w_(k) w_(k+1), . . . , w_(mod(k+n) _(SB) _(−1,N) _(cb) ₎, wherew_(k) is a soft bit received by the UE, and k is the smallest index ofthe indexes of the respective soft bits received by the UE. Thus, the UEcan keep soft bits in the soft buffer for each code block according tothe above method so as to support the retransmission operation of HARQwith incremental redundancy (HARQ IR).

It should be understood that when the base station processes a softbuffer based on any of the parameters M_(DL_HARQ) ^(real), M_(DL_HARQ)^(base), X and M_(DL_HARQ) ^(ref), the UE side can also process a softbuffer based on any of the parameters M_(DL_HARQ) ^(real), M_(DL_HARQ)^(base), X and M_(DL_HARQ) ^(ref). It shall be understood that the abovecombination can be joined and selected freely as required. If the basestation and the UE adopt the same parameter for processing a softbuffer, then the operation consistency can be kept; and if the basestation and the UE adopt different parameters for processing a softbuffer, then the optimization can be performed under differentconditions.

In step 402, the UE receives data distributed by the base station viaPDCCH and PDSCH.

The UE receives the PDSCH sent by the base station, performs operationsof rate de-matching, decoding, Cyclic Redundancy Checking (CRC), etc.,and when the PDSCH decoding verification fails, performs caching for thesoft bits of the PDSCH.

Further, an embodiment of the present invention is a method ofsupporting downlink transmission which includes the following steps: theUE receiving information sent by the base station via PDCCH and PDSCHaccording to the transmission resources allocated by the base station;and, afterwards, the UE feeding back HARQ-ACK information to the basestation according to the reference HARQ-ACK timing relation, wherein thereference HARQ-ACK timing relation defines the HARQ-ACK feedback timingof the subframes applicable to downlink transmission during actualrunning.

Specifically, the HARQ-ACK timing relation reuses a HARQ timing relationof uplink-downlink configurations in existing specifications.

Based on the above method, as shown in FIG. 5, the present inventionfurther discloses a device that includes a base station side device 100,a resource management module 110, and a sending module 120.

Specifically, the resource management module 110 is configured toallocate transmission resources for the UE and process a soft bufferaccording to a soft buffer parameter. The sending module 120 isconfigured to perform rate matching for a Physical Downlink SharedChannel (PDSCH) and send data to the UE via a Physical Downlink ControlChannel (PDCCH) and PDSCH.

Specifically, the resource management module 110 processes a soft bufferaccording to a soft buffer parameter, in which the selection of the softbuffer parameter includes any one of or multiple of the followingmethods.

The parameter for processing a soft buffer is an actual maximum numberof current downlink HARQ processes determined according to theuplink-downlink subframe distribution of a cell and the soft buffer isperformed according to the actual maximum number of current downlinkHARQ processes determined according to the uplink-downlink subframedistribution of the cell; the parameter for processing a soft buffer isa maximum number of downlink HARQ processes in the LTE release 8 definedby the basic TDD uplink-downlink configuration configured by SIB1broadcast information, and the soft buffer is processed according to themaximum number of downlink HARQ processes in the LTE Release 8 definedby the basic TDD uplink-downlink configuration configured by the SIB1broadcast information; the parameter for processing a soft buffer is apredefined fixed value of the maximum number of downlink HARQ processes,and the soft buffer is performed according to the predefined fixed valueof the maximum number of downlink HARQ processes; and the parameter forprocessing soft buffer is a maximum number of downlink HARQ processesdetermined according to a reference HARQ-ACK timing relation, and thesoft buffer is performed according to the maximum number of downlinkHARQ processes determined according to the reference HARQ-ACK timingrelation.

According to the above method, as shown in FIG. 5, an embodiment of thepresent invention discloses a user equipment (UE) 200 which comprises aresource management module 210 and a receiving module 220.

The resource management module 210 is configured to determineinformation of transmission resources allocated to it by a base stationand determine a parameter for processing a soft buffer; and thereceiving module 220 is configured to receive Physical Downlink ControlChannel (PDCCH) and Physical Downlink Shared Channel (PDSCH) sent by abase station according to the transmission resources and the parameterfor processing a soft buffer.

Specifically, the resource management module 210 processes a soft bufferaccording to the soft buffer parameter, wherein the selection of thesoft buffer parameter comprises any one of or multiple of the followingways: the parameter for processing soft buffer is a current actualmaximum number of downlink HARQ processes determined according to theuplink-downlink subframe distribution of a cell and the soft buffer isperformed according to the current actual maximum number of downlinkHARQ processes determined according to the uplink-downlink subframedistribution of the cell; the parameter for processing a soft buffer isa maximum number of downlink HARQ processes in the LTE release 8 definedby the basic TDD uplink-downlink configuration configured by SIB1broadcast information, and the soft buffer is processed according to themaximum number of downlink HARQ processes in the LTE Release 8 definedby the basic TDD uplink-downlink configuration configured by the SIB1broadcast information; the parameter for processing a soft buffer is apredefined fixed value of the maximum number of downlink HARQ processes,and the soft buffer is performed according to the predefined fixed valueof the maximum number of downlink HARQ processes; and the parameter forprocessing a soft buffer is a maximum number of downlink HARQ processesdetermined according to a reference HARQ-ACK timing relation, and thesoft buffer is performed according to the maximum number of downlinkHARQ processes determined according to the reference HARQ-ACK timingrelation.

The present invention, when changing the uplink-downlink subframeallocation, provide methods of processing a soft buffer of data duringHARQ downlink transmission. The present invention avoids confusion ofHARQ redundancy versions of data transmission between a base station anda UE, and optimizes the performance of HARQ soft combination. Thepresent invention does not affect a system's compliance, which isfulfilled efficiently and simply.

Modifications and changes can be made by those skilled in the artwithout departing from the scope of the present invention, and thesemodifications and changes should be construed as falling within thescope of the present invention.

The invention claimed is:
 1. A method of processing data performed by auser equipment (UE), the method comprising: receiving, through systeminformation block 1 (SIB1), a first uplink/downlink (UL/DL)configuration; obtaining a first maximum number of downlink hybridautomatic repeat request (HARQ) processes for the first UL/DLconfiguration; obtaining a first soft buffer size for a first code blockbased on a number of first code blocks divided from a first transportblock and a first parameter NIR associated with the first maximum numberof the downlink HARQ processes information; performing a HARQ softcombination based on the first soft buffer size; receiving, throughradio resource control (RRC) signaling, a HARQ timing relationinformation; identifying a change from the first UL/DL configuration toa second UL/DL configuration; after the change from the first UL/DLconfiguration to the second UL/DL configuration, obtaining a secondmaximum number of downlink HARQ processes for the second UL/DLconfiguration based on the reference HARQ timing relation; obtaining asecond soft buffer size for a second code block based on a second numberof code blocks divided from a second transport block and a secondparameter NIR associated with the second maximum number of the downlinkHARQ processes information; and performing the HARQ soft combinationbased on the second soft buffer size.
 2. A user equipment (UE), the UEcomprising: a transceiver configured to transmit and receive data; and acontroller configured to control: to receive, through system informationblock 1 (SIB1), a first uplink/downlink (UL/DL) configuration; to obtaina first maximum number of downlink hybrid automatic repeat request(HARQ) processes for the first UL/DL configuration; to obtain a firstsoft buffer size for a first code block based on a number of first codeblocks divided from a first transport block and a first parameter NIRassociated with the first maximum number of the downlink HARQ processesinformation; to perform a HARQ soft combination based on the first softbuffer size; to receive, through radio resource control (RRC) signalinga HARQ timing relation information; to identify a change from the firstUL/DL configuration to a second UL/DL configuration, to obtain, afterthe change from the first UL/DL configuration to the second UL/DLconfiguration, a second maximum number of downlink HARQ processes forthe second UL/DL configuration based on the reference HARQ timingrelation information, to obtain a second soft buffer size for a secondcode block based on a second number of code blocks divided from a secondtransport block and a second parameter NIR associated with the maximumnumber of the downlink HARQ processes, and to perform the HARQ softcombination based on the second soft buffer size.